北秦岭龙泉坪伟晶岩型高纯石英矿床黑云母成分特征及地质意义  

Biotite composition characteristics and geological significance of Longquanping pegmatitic type high purity quartz deposit in North Qinling Mountains

作　　者：郭峰 朱黎宽[1,3,4] 李建国 谭秀民 马驰[1,3,4] 张亮 王红杰[1,3,4] 张顺新 GUO Feng;ZHU Likuan;LI Jianguo;TAN Xiumin;MA Chi;ZHANG Liang;WANG Hongjie;ZHANG Shunzin(Zhengzhou Institute of Multipurpose Utilization of Mineral Resource,CAGS,Zhengzhou,Henan 450006,China;School of the Earth Sciences and Resources,China University of Geosciences Beijing,Beijing 100083,China;National Research Center of Multipurpose Utilization of Non-metallic Mineral Resource,Zhengzhou,Henan 450006,China;Engineering Technology Innovation Center for Development and Utilization of High Purity Quartz,Ministry of Natural Resources,Zhengzhou,Henan 450006,China)

机构地区：[1]中国地质科学院郑州矿产综合利用研究所,河南郑州450006 [2]中国地质大学(北京)地球科学与资源学院,北京100083 [3]国家非金属矿资源综合利用工程技术研究中心,河南郑州450006 [4]自然资源部高纯石英资源开发利用工程技术创新中心,河南商郑州450006

出　　处：《矿物岩石》2024年第4期71-82,共12页Mineralogy and Petrology

基　　金：国家自然科学基金项目(批准号:U2344206);中国地质调查局地质调查项目(编号:DD20221698);中国地质调查局花岗岩成岩成矿地质研究中心开放基金课题(编号:PM202310)。

摘　　要：高纯石英是高端技术领域的关键基础材料,近年来已成为一种战略性矿产资源。龙泉坪伟晶岩型高纯石英矿床位于北秦岭造山带东部,该矿床的赋矿围岩为秦岭群石槽沟组和峡河群寨根组,成矿岩石主要为白云母花岗伟晶岩。矿石中石英经选矿提纯后SiO_(2)含量为99.997%,且包裹体含量较低。本研究以龙泉坪高纯石英成矿伟晶岩为研究对象,利用电子探针对其中的黑云母开展主量元素分析,讨论成矿伟晶岩的形成环境,进而揭示高纯石英矿床形成机制。研究结果表明:成矿伟晶岩中黑云母具有高铝w(Al_(2)O_(3)=16.85%~17.58%,平均值为17.20%),低钛w(TiO_(2)=1.72%~2.02%,平均值为1.86%)和低镁w(MgO=4.49%~4.84%,平均值为4.72%)特征,属于铁叶黑云母。黑云母Ti含量温度计显示伟晶岩成岩温度为547-583℃(平均值为565℃),黑云母全铝压力计显示伟晶岩成岩压力为280~324 MPa(平均值为303 MPa),对应的成岩深度为10.60~12.26 km(平均值为11.44 km),暗示龙泉坪成矿伟晶岩具有中温、侵位深度大特征。黑云母成分结合区域地质资料显示,成矿伟晶岩为过铝质和壳源成因的S型花岗岩,形成于后碰撞伸展的大地构造背景。龙泉坪高纯石英矿床成因可能与成矿伟晶岩的中温(~565℃)和较大侵位深度(11.44 km)有关,板块折返引起的角闪岩相退变质作用导致石英内部杂质向晶界迁移,从而进一步提高了石英的纯度。The Longquanping pegmatitic-type high-purity quartz deposit,located in the eastern part of the North Qinling Orogenic belt,is hosted by the Shihaogou Formation of the Qinling Group and the Zhaigen Formation of the Xiahe Group.These host rocks primarily consist of muscovite granitic pegmatites.Anal-ysis indicates that the SiO_(2) content in the ore reaches 99.997% after purification,with minimal inclusions.This study focuses on the biotite within the ore-forming pegmatites,using electron probe microanalysis to investigate the biotite geochemistry further to explore the formation mechanism of the high-purity quartz deposit.The findings reveal that the biotite in the metallogenic pegmatites is characterized by high alumi-num(Al,,=16.85%-17.58%,average 17.20%),low titanium(TiO_(2)=1.72%-2.02%,average 1.86%),and low magnesium(Mg0=4.49%-4.84%,average 4.72%),classifying it as iron-leaf bio-tite.The biotite crystallization temperature ranges from 547 to 583℃(average 565℃),the crystallization pressure spans from 280 to 324 MPa(average 303 MPa),corresponding to depths between 10.60 and 12.26 km(average 11.44 km).These results suggest that the Longquanping metallogenic pegmatite formed under medium temperature conditions and at a substantial emplacement depth.Integrating these results with regional geological data suggests that the ore-forming pegmatite is a peraluminous,crust-de-rived S-type granite,formed in a post-collision,extensional tectonic setting.The genesis of the high-puri-ty quartz deposit at Longquanping is likely associated with medium crystallization temperature(565 C)and significant emplacement depth(11.44 km)of the ore-forming pegmatite.Additionally,hornblende-fa-cies metamorphism deriven by plate exhumation facilitated the migration of impurities within the quartz to grain boundaries,significantly enhancing its purity.

关 键 词：矿物成分 高纯石英 伟晶岩 黑云母 龙泉坪 北秦岭 

分 类 号：P574[天文地球—矿物学]